C > W generally. On deadline day, though, supply and demand takes over. There is a limited supply of centers, but the sense I get reading HF is that none of the true contenders (Boston, Washington, Pittsburgh, Tampa, St. Louis) have a real need for one. The demand is at the bubble (New York, Columbus and Winnipeg stand out). However, those teams are less inclined to give up a high pick because of the risk of things going south and that turning into a mid-1st or worse.
There is limited supply of wingers as well. There is demand among the true contenders; Pittsburgh and Boston, in particular, need a winger like Kreider.